- A complete tech branch of econ-enhancing techs and buildings (Trade center, Market center, Bank, Stock market....),
The same is true for Manufacturing, Research, Farming and Morale. The only area that gets less upgrades is Influence, which would definitely be a balance thing. And they all get bonus tiles, economy doesn't.
- a government branch, that gives 10%, 20% and 30% econ bonus,
True, if you don't mind making some compromises in your ability to wage war with another race.
- a green resource that give bonuses to econ,
And also one for Research, Morale and Influence. And we now have Asteroids for Manufacturing.
- trade ships that establish trade routes,
And production bonuses simply from having a moon in orbit, and research bonuses for having rings. Granted they aren't as much as you get from trade routes, but they're still represented. And you don't have to anything for them, they're automatic.
- the economic treaty and
Again, if you don't mind making military compromises.
- just simple selling your stuff for money
Provided you don't upgrade your ships instead of selling them off. Which is what I prefer to do.